Singulation, the process of separating a semiconductor wafer substrate into individual integrated circuit dies, is an essential procedure in semiconductor device manufacturing. Numerous methods can be used to achieve singulation including: laser cutting, scribe and break, routing, dicing or combinations thereof. One of the most commonly used methods for singulation is dicing. Dicing refers to cutting the wafer substrate along a street or kerf located between the dies via mechanical grinding with a rotating blade.
Shrinking integrated circuit geometries and the introduction of new materials into integrated circuit designs are present new challenges to existing singulation technologies. To facilitate faster device operating speeds and reduced power consumption, present and future generations of integrated circuits have decreasingly smaller circuit features and multiple layers of transistors, metalization and insulators made of low dielectric constant materials (e.g., dielectric constant less than ˜4). Unfortunately, the insulating layers of low dielectric constant materials have weak mechanical strength and poor adhesion to other layers of the integrated circuit. Moreover, to further improve integrated circuit performance, traditional silicon-based semiconductor wafers are being replaced by more fragile materials. Small multilayered circuit geometries on fragile substrate wafers are highly susceptible to peeling and chipping during conventional singulation. Reduced yields of high quality functional semiconductor devices, due to peeling and chipping of the integrated circuit dies, can significantly increase semiconductor device manufacturing costs.
Previous efforts to reduce the occurrence of peeling and chipping during singulation are not entirely satisfactory. Traditionally, seal rings, comprising metal lines, are formed around the perimeter of each die. Although the seal rings act as a barrier to help prevent micro-cracks from encroaching into dies during singulation, there can still be substantial losses of dies due to cracking and peeling under the seal ring. In other instances, singulation involves a combination of laser ablation and dicing. A laser ablation step fuses the circuit feature layers together, creating a metalized border along the streets. The metalized borders supplement the function of metal seal rings to further reduce micro-crack formation during a subsequent dicing step, to complete the separation of the wafer into individual dies. Laser ablation, however, can cause thermal damage to integrated circuits, resulting in lower yields of functional devices. In addition, laser ablation tools are substantially more expensive than dicing tools, thereby adding significant costs to the manufacture of semiconductor devices. Furthermore, semiconductor device production throughput is decreased because a semiconductor wafer ready for singulation has to be transferred to a laser ablation tool, and then transferred to a dicing tool.
Accordingly, what is needed in the art is an inexpensive method of manufacturing semiconductor devices that minimizes the losses of integrated circuits from chipping and peeling of dies during singulation.